In recent years, a vehicle-to-vehicle communication system has been proposed in which each of multiple vehicles sequentially broadcasts a communication packet (hereinafter referred to as a vehicle information packet) indicating vehicle information such as a current position, a traveling speed, or a traveling direction, and sequentially receives a vehicle information packet transmitted from another vehicle.
As a mode of a communication between vehicles (that is, vehicle-to-vehicle communication) in the vehicle-to-vehicle communication system described above, as disclosed in Patent Literature 1, a mode of directly transmitting and receiving the vehicle information packet between the vehicles over no wide area communication network has been assumed. The direct wireless communication between the vehicles is realized by employing a CSMA/CA (carrier sense multiple access/collision avoidance) method as an access control method.
In addition, vehicle information on the other vehicles obtained by the vehicle-to-vehicle communication is used for a vehicle control that assists driving operation of a driver, a self-driving, information providing to the driver, and the like. For that reason, the vehicle information acquired by the vehicle-to-vehicle communication needs to be real-time information as close as possible to a current situation. In view of such a demand, a transmission cycle of the vehicle information packet is set to several hundred milliseconds (more specifically, 100 milliseconds) in many cases.